I am asking this question after reading through most of the related/relevant question-answers and I believe my query is not a duplicate. Please highlight otherwise and my apologies if it is so.
My in-laws are in the UK now on a visitor visa that expires on 1 Nov 2017. They are having to leave the UK soon to attend a family emergency back in India (death of a close relative- follow up rituals take 13-15 days) and they want to be with the relative's family for an extended period in India. For this reason, I am planning to bring them back by Feb-Mar, by applying for another visitor visa. I am assuming this will be risk-free as I've heard of a certain unwritten rule of a 6 month cooling off period.
Now, my query is- is the 6-month cooling off period from the day the visitor visa expires?- in which case they can only apply for a visitor visa with a tentative travel date on or after 2 May 2018
Is the 6-month cooling off period from the time they leave UK? in which case they can apply for a visitor visa for a travel date that is 6 months from the date they leave UK, tentatively (if they leave mid-June 2017) early Jan 2018.